/*
 * Copyright © 2019 Collabora Ltd
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include "nir.h"
#include "nir_builder.h"

/** nir_lower_point_size_mov.c
 *
 * This pass lowers glPointSize into gl_PointSize, by adding a uniform
 * and a move from that uniform to VARYING_SLOT_PSIZ. This is useful for
 * OpenGL ES level hardware that lack constant point-size hardware state.
 */

static void
lower_point_size_mov_after(nir_builder *b, nir_variable *in)
{
   nir_def *load = nir_load_var(b, in);
   load = nir_fclamp(b, nir_channel(b, load, 0), nir_channel(b, load, 1), nir_channel(b, load, 2));
   nir_store_output(b, load, nir_imm_int(b, 0),
                    .io_semantics.location = VARYING_SLOT_PSIZ);
}

static bool
lower_point_size_mov(nir_builder *b, nir_intrinsic_instr *intr, void *data)
{
   nir_variable *var = NULL;
   switch (intr->intrinsic) {
   case nir_intrinsic_store_output:
   case nir_intrinsic_store_per_vertex_output:
   case nir_intrinsic_store_per_view_output:
   case nir_intrinsic_store_per_primitive_output: {
      nir_io_semantics sem = nir_intrinsic_io_semantics(intr);
      if (sem.location != VARYING_SLOT_PSIZ)
         return false;
      break;
   }
   default:
      return false;
   }
   b->cursor = nir_after_instr(&intr->instr);
   lower_point_size_mov_after(b, data);
   if (var && !var->data.explicit_location)
      nir_instr_remove(&intr->instr);
   return true;
}

bool
nir_lower_point_size_mov(nir_shader *shader,
                         const gl_state_index16 *pointsize_state_tokens)
{
   assert(shader->info.stage != MESA_SHADER_FRAGMENT &&
          shader->info.stage != MESA_SHADER_COMPUTE);
   assert(shader->info.io_lowered);

   bool progress = false;
   nir_metadata preserved = nir_metadata_control_flow;
   nir_variable *in = nir_state_variable_create(shader, glsl_vec4_type(),
                                                "gl_PointSizeClampedMESA",
                                                pointsize_state_tokens);
   if (shader->info.outputs_written & VARYING_BIT_PSIZ) {
      progress = nir_shader_intrinsics_pass(shader, lower_point_size_mov, preserved, in);
   } else {
      nir_function_impl *impl = nir_shader_get_entrypoint(shader);
      nir_builder b = nir_builder_at(nir_before_impl(impl));

      lower_point_size_mov_after(&b, in);
      shader->info.outputs_written |= VARYING_BIT_PSIZ;
      progress = true;
      nir_progress(true, impl, preserved);
   }
   return progress;
}